The present invention relates to a storage tank and, more particularly, to a storage tank for storing a radioactive substance or the like at a nuclear power plant or the like, as well as to a method for manufacturing the same.
In general, radioactive waste produced at a nuclear power plant or the like is stored in a storage tank to attenuate radiation. As a storage tank of this type, a so-called lined storage tank is used wherein the inner surface of a storage tank main body of concrete having the ability to block radiation is lined with lining plates such as stainless steel plates. A lined storage tank of this type is conventionally constructed in the manner as shown in FIG. 1. Referring to this figure, symbol A denotes a storage tank main body of concrete which has sufficient thickness to block radiation and which is integrally formed with a building facility of the nuclear power plant. Lining plates B such as stainless steel plates are lined on the inner wall of the storage main body A to a position slightly above the upper limit of the fluid level of the radioactive waste. An inlet pipe C and an outlet pipe D are connected to the storage tank through the storage tank main body A and the lining plates B so that the radioactive waste is introduced inside the storage tank from the inlet pipe C and is taken out via the outlet pipe D. A number of support members E project from the inner wall of the storage tank main body A at the upper edges of the lining plates B. A separation wall F is mounted on these support members E. This separation wall F is made of reinforced concrete and is capable of blocking radiation. This separation wall F separates the interior of the storage tank into two compartments. Symbol G denotes a manhole. Main parts of the equipment in the storage tank, such as measuring equipment H and a storage tank interior agitating pump I, extend through the upper separation wall F and are arranged thereon. A manhole J is arranged at the ceiling portion of the storage tank main body A. An operator K descends from this manhole J onto the separation wall F for performing maintenance and inspection of the measuring equipment H and the storage tank interior agitating pump I. The recent trend in nuclear plants is toward bigger capacity. With such a trend, the amount of radioactive waste increases and the capacity of storage tanks to store it must also be increased. However, with the storage tank of the construction as described above, the upper space separated by the separation wall F cannot be utilized as space for storing the radioactive waste, thus limiting the capacity of the storage tank. Especially in the case of a nuclear reactor, the building cannot be made very big due to earthquake design standards, so that the size of the storage tank is also limited. In order to solve this problem, it has been proposed to store as much radioactive waste material as possible inside the storage tank by storing together solid waste L and liquid waste M as shown in FIG. 1. However, even with this measure, the amount of waste material which can be stored is still limited and an improvement in the volume efficiency of the storage tank itself has been desired.